1. Field of the Invention
The present invention relates to a DSRC (dedicated short-range communication) car-mounted equipment used for an ETC (electronic toll collection) system in an ITS (intelligent transport system). More specifically, the invention relates to a DSRC car-mounted equipment which automatically checks, in advance, disorder in the communication caused by a drop in the radio communication power level (communication ability) of the main body of the car-mounted equipment and alarms the driver in case disorder has occurred.
2. Prior Art
In a DSRC car-mounted equipment used for a toll collection system such as ETC, in general, the main body of the car-mounted equipment having an antenna unit is usually installed near a dashboard (on or in the dashboard) in the compartment in order to transmit and receive signal waves of a sufficient degree of level to and from a radio equipment in an on-the-road equipment on the road side.
Further, a control unit in the main body of the car-mounted equipment is so constituted as to establish a communication circuit relative to the on-the-road equipment by receiving signal waves from the radio equipment of the road side through the antenna unit of the car-mounted equipment and, then, transmitting signal waves toward the radio equipment of the road side.
Usually, therefore, the DSRC car-mounted equipment remains in a state of receiving signals from the on-the road equipment.
In particular, the conventional DSRC car-mounted equipment is not equipped with means for checking the antenna unit of the car-mounted equipment and, hence, remains in a state of receiving signals irrespective of the conditions in the compartment or the state of installing the antenna unit of the car-mounted equipment.
As is well known, on the other hand, the DSRC car-mounted equipment used for the toll collection system is based on a dedicated short-range communication and, hence, the antenna unit of the car-mounted equipment exhibits a sharp directivity toward the radio equipment of the road side that is located at a position higher than the vehicle.
Therefore, when a driver carelessly puts an obstacle (book or clothing) that may interrupt the propagation of electromagnetic waves on the antenna unit of the car-mounted equipment, or when the antenna unit of the car-mounted equipment is installed in an extremely inclined manner at the time of mounting the main body of the car-mounted equipment, the signal waves from the radio equipment of the road side are not sufficiently received by the antenna unit of the car-mounted equipment, which may cause a fatal hindrance to the communication function of the main body of the car-mounted equipment.
That is, when the signal waves from the radio equipment of the road side are not received due to an obstacle placed on the antenna unit of the car-mounted equipment, the conventional DSRC car-mounted equipment is not capable of detecting the obstacle. Therefore, despite the vehicle enters into the communication region with the on-the-road equipment, the standby state for receiving signals continues and the communication circuit may not be established.
Similarly, when the antenna unit of the car-mounted equipment is installed being conspicuously inclined, the reception power level (reception intensity) greatly decreases for the antenna unit of the car-mounted equipment, and the communication circuit may not be established, either.
When the vehicle has entered into the automatic toll collection lane on a toll road, the toll collection function is invalidated since no communication circuit is established between the antenna unit of the car-mounted equipment and the radio equipment of the road side and, hence, the vehicle must be forcibly stopped in the automatic toll collection lane.
In order to solve the above-mentioned problem, Japanese Unexamined Patent Publication (Kokai) No. 11-64416 proposes a device for checking the car-mounted equipment.
According to the device disclosed in the above publication, however, a worker must move to a place where the checking device is installed to check disorder of the car-mounted equipment, lacking practicability.
As described above, the conventional DSRC car-mounted equipment is not provided with means for checking the communication ability of the antenna unit of the car-mounted equipment. Therefore, the driver cannot recognize the disorder in the antenna unit of the car-mounted equipment despite the signal waves from the radio equipment of the road side may not have been received to a sufficient degree by the antenna unit of the car-mounted equipment, and the communication is not accomplished with the radio equipment of the road side, causing various inconveniences.
The present invention was accomplished in order to solve the above-mentioned problem and has an object of providing a DSRC car-mounted equipment which automatically checks disorder in the antenna unit of the car-mounted equipment due to a drop in the communication ability, and informs the driver of disorder in the antenna unit of the car-mounted equipment to prevent the occurrence of inconvenience in advance.
The DSRC car-mounted equipment according to the invention comprises:
a main body of a car-mounted equipment having a control unit and an antenna unit for executing radio communication with an on-the-road equipment installed on a road on which a vehicle travels;
information output means connected to the control unit;
a checking unit arranged in the vehicle so as to be positioned between the antenna unit of the car-mounted equipment and a radio equipment of the road side of the on-the-road equipment, and having a checking circuit unit and a checking antenna unit for executing radio communication with the antenna unit of the car-mounted equipment; and
an antenna-judging means for judging the communication ability of the antenna unit of the car-mounted equipment based on the communication state of check signal waves between the antenna unit of the car-mounted equipment and the checking antenna unit; wherein
the antenna-judging means produces an alarm signal when the communication ability of the antenna unit of the car-mounted equipment is smaller than a predetermined value; and
the control unit of the car-mounted equipment drives the information output means in response to the alarm signal to produce an alarm.
In the DSRC car-mounted equipment according to the invention, the antenna-judging means produces an alarm signal when the reception intensity at the checking antenna unit of the check signal waves transmitted from the antenna unit of the car-mounted equipment is smaller than a predetermined value.
In the DSRC car-mounted equipment according to the invention, the antenna-judging means produces an alarm signal when the reception intensity at the antenna unit of the check signal waves transmitted from the checking antenna unit is smaller than a predetermined value.
In the DSRC car-mounted equipment according to the invention, the intensity for transmitting the check signal waves is set to a value smaller than a normal transmission intensity of from the antenna unit of the car-mounted equipment to the radio equipment of the road side.
In the DSRC car-mounted equipment according to the invention, the check signal waves are transmitted when the power source circuit is closed.
The DSRC car-mounted equipment according to the invention further comprises a vehicle speed detector unit for detecting the speed of a vehicle, and a stop-judging means for judging the halted state of the vehicle based on the vehicle speed, wherein the check signal waves are transmitted when the vehicle is brought into a halt.
In the DSRC car-mounted equipment according to the invention, the information output means includes at least either a display unit or a voice output unit.
In the DSRC car-mounted equipment according to the invention, the main body of the car-mounted equipment is arranged near the dashboard of the vehicle, and the checking unit is arranged near the windshield of the vehicle.
The DSRC car-mounted equipment according to the invention further comprises a cable for electrically connecting the main body of the car-mounted equipment to the checking unit, wherein the control unit of the car-mounted equipment transmits a check signal wave transmission timing to the checking unit through the cable.
In the DSRC car-mounted equipment according to the invention, the checking unit is isolated from the main body of the car-mounted equipment, and the equipment control unit of the car-mounted equipment transmits a check signal wave transmission timing to the checking unit by radio communication.
In the DSRC car-mounted equipment according to the invention, the antenna-judging means produces an alarm signal when no response signal is obtained from the checking unit at the time of transmitting the check signal waves.
In the DSRC car-mounted equipment according to the invention, the control unit of the car-mounted equipment transmits and receives data related to the toll collection to and from the on-the-road equipment installed on a toll road, and automatically receives the toll based on the data related to the toll collection.